1. Field of the Invention
The present invention related to an apparatus for increasing the image space frequency, and more particularly to an nonsquare crystal structure for increasing the sample frequency of scanning in a charge-coupled device (CCD) scanning apparatus.
2. Description of the Prior Art
As illustrated in FIG. 1, a light-sensitive device 10 consists of a charge-coupled device (CCD) 12. CCD 12 has three scanning lines, one is red color scanning line (R), another is green color scanning line (G), and the other is blue color scanning line (B). Each of the three scanning lines consists of a plurality of crystals 14, and the three scanning lines are used for scanning and transforming an image into three electrical signals representative of the red portion, green portion, and blue portion of the image, respectively. As illustrated in FIG. 2A, it shows a plane view of the conventional square crystal structure (x=y=1 pixel width), wherein x is the vertical dimension and y is the lateral dimension. The conventional CCD scanning apparatus consists of a plurality of square crystals, and the feature of the square crystal may be a square, a polygon or a circle. Actually, the square crystal is a square structure in the ratio between vertical dimension x and lateral dimension y, and the vertical dimension of the square crystal structure is equal to the lateral dimension of the square crystal structure approximately 1 pixel width. For example, the feature of the square crystal structure of the conventional scanner is square, as illustrated in FIG. 3A, the conventional scanner moves along the forward direction (y direction) at a uniform velocity. As illustrated in FIG. 3B and FIG. 3C, during the conventional scanner with the square crystal structure scanning, a sample Width 32 gotten by a sample uni-integral area 30 is very wide about 2 pixel width. In addition, the image space frequency gotten by the sample integral areas via the theorem such as sample theorem and Fourier transform is limited. Therefore, the limited image space frequency influences the quality of the image. As illustrated in FIG. 4A, if a series of the original image pixel values are "100, 0, 100, 0, . . . ", then, as illustrated in FIG. 4B, the series of the image pixel values will be "50, 50, 50, 50, . . . " in accordance with the result of the image sample integral area calculated after scanning by the conventional scanning apparatus using the square crystal structure(x=y=1 pixel width). Therefore, the conventional scanning apparatus will result in high distortion in the quality of the image.